1. Field of the Invention
The present invention relates to improvement of an impeller for realizing a centrifugal fan capable of responding to needs of a smaller and high-performance centrifugal fan.
2. Description of the Related Art
A centrifugal fan, which is frequently used for cooling heated components in office automation equipment or the like, is surely required to be improved, with needs for a smaller, high-performance, and a low cost device mounting the centrifugal fan. Therefore, the improvement of an impeller, which largely affects a noise when operating and a cooling of a heated component internally mounted to the centrifugal fan, is also required.
The related art documents, Japanese Patent Applications Laid-Open Nos. 2001-140791 and 11-218096, also are required to solve the above-described problems. Although it is not described in detail, the improvement of connecting structures on a shroud side and on a hub side is suggested so as to ensure stiffness of a blade while maintaining an aerating function, and to make fabrication of the blade, which maintains stiffness, easier. Each of the related arts is effective to a certain degree, but needs for the smaller and high-performance device is not limited, and there is still room for further improvement.
Hereinafter, the conventional centrifugal fan will be described with reference to FIG. 5.
FIG. 5 is a cross-sectional view of a centrifugal fan according to the related art.
A centrifugal fan 10 shown in FIG. 5 is mainly composed of a casing 12, a motor 13, a control circuit 14 and an impeller 15.
And the impeller 15 is mainly composed of a blade 15-1 and a hub 15-2.
And, in FIG. 5, reference numeral 12-1 denotes a suction opening.
In the conventional centrifugal fan 10, the hub 15-2 is provided on an end portion of the blade 15-1 so as to extend on inner and outer diameters thereof, and a connecting ring 15-4 is provided on an outer peripheral surface on a shroud side thereof, as means for ensuring stiffness of the blade 15-1.
A problem to be solved in the centrifugal fan 10 according to the above-described related art is to maintain stiffness of the blade 15-1, which may cause a noise when operating, and to realize a more effective cooling in response to an increase of heat generation of internally mounted components, with needs for the smaller and high-performance device.